alesis midiverb ii

 

inside

dsp

q&a

psu

 

 

 

 

 

 

 

 

 

 

Markings on the chip (next to Texas Instruments logo) say: CF61252FN  N  48816  8715. Googling doesn't help. The hint from a guy at Wavefront Semiconductor (that used to be Alesis Semiconductor before breakup) says that the specs were never released to public and probably no schematics or datasheets have survived even within the company. DSP chip in early MidiVerbs later evolved into Alesis SCR (Single Chip Reverb) giving some hints about what might be inside the MidiVerb DSP. If anyone could shed some light on the inner workings of the MidiVerb DSP chip (eg. in form of a data sheet!!) I would be almost eternally thankful.

The chip itself is a 68 pin PLCC. Poking around with DVM suggests the following pinout:

Pin Function
1 GND
2-9, 61-68 Sample memory data bus D0-D15 (16 bits)
10-17, 19-26 Data bits for Digital-to-Analog Conversion (16bit sample)
18 VDD
27 Analog demultiplexer INHIBIT signal
28 Voltage comparator output (End of conversion)
29 GND
30 8 MHz DSP internal system clock
31  
32 OVLD (Overload) indicator control
33-34, 36-41 Program memory data bus D0-D7 (8 bits)
35 GND
42-49 Program memory address bus A0-A7 (8bits). A0 is also used as -RAS for DRAM. A5 is also used as 'deglitcher' control signal in analog demultiplexer.
50 -WR (DRAM)
51 -CAS (DRAM)
52 VDD
53-60 Sample memory address bus A0-A13 (14 bits, multiplexed)